1. Field of the Invention
The present invention relates generally to waste removal systems and more particularly to systems for removing nuclear waste from a storage silo.
2. Description of the Prior Art
It is known to use long-reach arm devices to reach into tanks or silos through small openings to sample or remove waste. Many of these devices have been sponsored and developed by the Department of Energy to deal with tank and silo waste cleanup problems.
At Oak-Ridge National Labs, a Spar Light Duty Utility Arm (LDUS) has been used to manipulate a sleucing head to remove waste material from the GUNITE tank farm. The SPAR arm was deployed from a tower enclosure that is longer than the arm. Access to the tank was an opening approximately two feet in diameter and the vertical and horizontal reach was approximately 40 feet. The Spar LDUA arm is an 8 ft. hydraulically actuated arm with a general-purpose gripper on the arm end. The gripper was used to hold a sleusing head that was deployed through a separate opening in the tank. The sluicing head was partially supported by an auxiliary actuated pipe structure to hold the weight and to convey the waste material out of the tank. The pipe structure and sleucing head also required a tower enclosure as long as the sleucing pipe.
A truckxe2x80x94deployed version of the arm has also been developed. This is a similarly designed arm but is designed for deployment from a large truck platform. An ancillary truck structure must be used for a sleucing head or alternative waste conveyance system that is required to actually remove waste or do any work.
Grey Pilgrim Company has developed a cable-driven arm, EMMA that features a large working channel through the center of the structure. This device also requires an auxiliary structure for the waste conveyance tube. The Grey Pilgram arm has been well studied and well publicized in the literature, however, there are no known successful deployments of the arm, to date, on large sized structures.
In the concrete industry, the grain industry, the coal industry, and other commercial industries requiring vacuum conveyance of dry material, large, long-reach hydraulic arms are commonly used. These arms, however, do not require special enclosures to contain radioactive material, and need not be deployed through very small openings in the tank or silo.
Nuclear waste removal systems are also documented in numerous U.S. Patents some of which are mentioned below.
U.S. Pat. No. 5,782,209 teaches a segmented automated nuclear waste removal lance where the individual segments are connected by pins to form a rigid lance inside the reactor. There is no vacuuming of the sludge; instead there is a blowing of the sludge from the tubes and reactor plates by the segmented lance. Also, there is no teaching of individual linked clamshell segments enclosing the working cables and the vacuuming tube of the system.
U.S. Pat. Nos. 5,219,470 and 4,715,324 teach vacuuming nuclear waste sludge removal systems. However, there is no teaching of any design for enclosing the working elements of the system including the vacuum line to shield from radioactivity.
A careful review of the prior art thus shows that while segmented nuclear waste removal systems may be known a design of linked segments for same which would be properly shielded from emitting radioactivity was needed.
The present invention solves the problems associated with prior art devices as well as others by providing a Revolving Turret Reeled cable incremental link Extending Vacuuming Robot (ReTRIEVR). The robot system is deployed from a gantry structure to break up and vacuum waste from the confined-space Silo-3 structures. Silo-3 is an 80-ft diameter 35-ft high domed structure housing dry powdery or granular metal oxide waste byproducts from processing concentrated uranium ore in the early days for the US nuclear program.
The ReTRIEVR is a long-reach robot that combines a segmented-link-mast (xcx9c60 feet long) with an industrial Master-Slave robot on the mast end. Each link measures approximately 17 inches in diameter by 10 feet in length. A longitudinal hinge along the link permits clamshell closure around the working cables. The clamshell halves are latched together by a linear array of captive screws. Adjacent links are joined by a transverse hinge pin, and the two hydraulic cylinder connecting pins. Extending and retracting the hydraulic cylinders achieve active articulation. The ReTRIEVR robot is inserted through a 20-inch access hole in the center of the silo dome.
The end of the link platform features a six degree-of-freedom, hydraulically operated, dexterous robotic arm. The arm can hold and maneuver a vacuuming tube, a delumping tool, a fixative spray tool, and other tools that may be required to assist in waste retrieval. The mining strategy is to vacuum as much material as can be reached from a fixed mast position. The dexterous robot action followed by mast repositioning is repeated until the entire silo is emptied. After the bulk of the material is emptied, an air sweeper will aid the final removal and fixative spray will be fogged into the silo to seal any remaining contamination.
A turret assembly rotates both the arm and the system cables. A video Pan-Tilt-Zoom camera is installed under the turret before the arm is inserted to provide an overview of mining activities. The turret assembly acts on substantial bearings to keep arm loads away from the silo roof. The rotating turret sleeve is inserted just through the silo roof within a fixed flexible seal that joins the silo to the gantry enclosure.
A reeled cable drum assembly sits atop the turret to manage the vacuum hose, and the control umbilical cable. This assembly includes a steel cable winch that passes through the links and connects to the robotic arm base. The drums are driven by the winch motor through slip-clutch assemblies to keep tension on the cables at all times without an independent motor.
The mast and arm are deployed from a contamination-barrier gantry enclosure mounted atop a gantry structure that spans the silo. This gantry enclosure is large enough to support personnel to manually add and remove links, to decontaminate the ReTRIEVR system and to perform any repair or maintenance that may be required.
The control system is located within 150 feet of the gantry-enclosure. At the control station, a robotic arm master is used to manipulate the dexterous slave robotic arm. A set of switches is also available for xe2x80x9cjoint-by-jointxe2x80x9d control of the link hydraulic valves, the winch, turret, PTZ video, etc. Link valves are controlled with a 3-position switch to xe2x80x9cextendxe2x80x9d, xe2x80x9cretractxe2x80x9d, or xe2x80x9choldxe2x80x9d (no active servo positioning).
In view of the foregoing it will be seen that one aspect of the present invention is to provide a robot required a relatively small enclosure since the segments are attached and removed as the arm is lowered or raised.
Another aspect is to provide a robot having a central channel large enough to support large diameter vacuum hose.
Yet another aspect is to provide a robot having a conveyance system protected by clamshell mast links.
Still yet another is to provide a robot wherein the turret and gantry structure take all loads from the arm to have no loads imposed on the silo opening.
Still yet another is to provide a robot where practically all conceivable failure modes of the arm permit arm removal from the silo in accordance with the normal removal practice.